That is because they accepted faith with their tongues then disbelieved with their hearts, therefore their hearts were sealed – so now they do not understand anything.
यह इस कारण कि वे ईमान लाए, फिर इनकार किया, अतः उनके दिलों पर मुहर लगा दी गई, अब वे कुछ नहीं समझते